New cars versus old cars. CO2 versus recycling.

We've found the answer to my Peugeot 106 question. Until now we have struggled to get sensible data on the emissions of older cars. The question was driven by the fact that my partner's car is a rocking drive around London and hardly seems to use any fuel but is ten years old and would never be a candidate for congestion charge or parking exemption like a Prius or G-Wiz is.

But here is a database that covers vehicles up to ten years' old. The 1997 Peugeot 106 XN produces 154g/km, a Prius is around 104g/km, a 2002 Focus 1.4CL is 162g/km, a Mini One (the just replaced one) is 160g/km and the diesel manual (I'm being nice) Jeep Grand Cherokee is 276g/km. So Parisian students and district nurses of the world rejoice - the 106XN is pretty clean. Joe smugly points out that a new BMW 120i (which is very fast) produces less CO2 than the Peugeot, but others would point out that manufacturing a new car typically requires 400,000 litres of water. And we'll have to crush and bury the 106. And I'd rather drive around in a 106 than a BMW 120i anyway as I would look like a middle manager at Barnard Marcus.

The issue of new versus old is likely to become a hot topic, as people start to ask whether upgrading an existing vehicle is more responsible than replacing it. So too is an impending sense that we might not necessarily choose the same things in future that we do right now. A friend mentioned to me the other day that her daughter had just bought an SUV "because she said it was probably the last chance she'd have to get away with driving something that big in London".

Most of these Hillman Imps, seen here at the ill-fated Linwood plant in Glasgow, won't have survived the seventies, despite 'the most up to date paint shop in Europe'. Cars from the mid 90s are a different proposition.

The reliability of modern cars was transformed through the introduction of engine electronics during the mid-1980s and cars now have the potential to last far longer than the global infrastructure of car manufacturing plants would see as ideal. Might people start to focus on maintaining old vehicles to pass emissions tests rather than replace them? Similarly, might customisation of old vehicles get into vogue as the fashionable eschew the new for the recycled?

If you've read the likes of Bill McDonough, who argues we have to fundamentally rethink the way products are designed, sold and taken back in order to properly address sustainability you might agree that factors beyond CO2 count. As a taster for some of the things we're going to examine in more detail over time, this is what the Financial Times had to say on the topic of water use (sub rqd) during manufacture last Tuesday:

Few people, when they slice up a tomato for a sandwich, or tuck into an apple, give a thought to the amount of water that went into the production of those foods. But the water that we consume indirectly, through the food we eat and goods that we use, dwarfs our water consumption for drinking and washing. About 70 per cent of the water consumed by people in the UK, for example, comes from overseas, according to Waterwise, a UK government- funded body that aims to reduce water usage by businesses. It is imported in the form of food, clothing, computers and cars. These imports give people in developed countries a far higher "water footprint" than people in poor countries. Take that tomato. About 13 litres of water went into its cultivation. The apple took about 70 litres to grow. And the hamburger represents a whopping 2, 400 litres of water. The water used in growing food, making textiles or manufacturing consumer goods is variously known as "embedded water", "hidden water" or "virtual water". In the past few years, water experts have begun to focus more attention on how much water is used in this way, and the inefficiencies in the production of goods that embedded water can reveal, as well as on how the trade in embedded water between nations can lead to paradoxical situations in which dry countries end up exporting water, in the form of goods, to wetter places.

Just as I was starting to wrap my head around CO2, and then food miles, now there's the topic of embedded water to consider. Wow.

(If you fancy reading more about how the auto industry transformed reliability a few decades ago, LJK Setright's fabulous book 'Drive On! A social history of the motor car' is the place to go). Joe would tell you that the whole reliability thing has gone tits-up since the advent of extremely complex electronic control systems of the likes we've seen more recently. Nerd moment over.)